1. Field of the Invention
This invention relates to polymerizable unsaturated polyester resin syrup compositions, to methods of curing such polymerizable unsaturated polyester resin syrup compositions in the presence of significant quantities of aqueous alkali stabilized colloidal silica, and to the thermoset products obtained thereby.
2. Description of the Prior Art
Unsaturated polyester resin syrups are employed in the production of coatings, molded, cast and hand-lay-up products such as flat and profiled building sheets, automobile fenders and other shaped components, furniture, plumbing fixtures, duct work, boats, electrical component housings, electrical circuit boards, and the like. The unsaturated polyester resin syrups are frequently reinforced with fibrous fillers, customarily glass fibers and may be extended with inert particulate fillers such as wood flour, silica, glass beads, clay calcium carbonate and the like. See "Polyesters and Their Applications", Bjorksten et al., Reinhold Publishing Corporation, New York 1960 (4th printing).
Unsaturated polyester resin syrups also have been extended by dispersing water in the resin in the form of small droplets. Such emulsions have been described as containing 40 to 85 per cent by weight water in combination with 15 to 60 per cent by weight of unsaturated polyester syrups. See U.S. Pat. No. 3,591,191. Compositions containing 50 to 80 per cent by weight of water in a mixture of water and unsaturated polyester resin syrup are described in U.S. Pat. No. 3,687,883.
Small quantities of silica aerogel have been employed as thickeners for unsaturated polyester resins, U.S. Pat. No. 2,610,959.